An Improved Acid Fracturing Design through RoqSCAN Technology: A Case Study from Daniudi Gas Field in Ordos Basin, China
Round 1
Reviewer 1 Report
I have carefully read this paper. This paper investigated the acid fracturing technology by using fine formation evaluation with the RoqScan tool. Based on the device, the elements, minerals, and some rock mechanical parameters of the target formation were evaluated. Moreover, the fracturing design was also performed on the basis of fine formation evaluation and fine modeling. This manuscript topic is of interest for "Processes" and the authors performed an effort in acid fracturing by using fine formation evaluation. The authors may offer a work that potentially can improve our knowledge about the acid fracturing technology. The authors should address the following issues before this manuscript is considered for publication.
- This paper focuses on acid fracturing investigations. Please add relevant references in the introduction section.
- The RoqScan tool is very convenient and useful. The description of Figure 2 is short. Please add more descriptions.
- Figure 1 and Figure 2 contain some Chinese. Those contents should be written in English.
- Effective acid-etched fracture and acid-etched fracture conductivity are the two key factors that determine the acid fracturing efficiency. Please describe in detail the simulation of these two factors in the acid fracturing design and their guiding significance for subsequent stimulation in the field.
- Please revise some grammar errors and polish the language. Some issues are shown as follows:
Line 10: "completion, fracturing, and production"
Line 15: "principle", "minerals"
Line 34: "exploration and development, holding more than 60% of the world’s oil"
Line 220: "the geological grid model, lithofacies model, and natural fracture model"
Line 247: "the parameters, including porosity"
Line 258: "increases the stimulated reservoir volume"
Line 272: "promotes uniform fracture initiation and propagation"
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors investigated acid fracturing design by using fine formation evaluation: a example from daniudi gas field in ordos basin. The authors used a novel tool ROQSCAN for fine reservoir characterization. However, motivation behind this research is very weak because most of the findings of this paper have already been reported in the literature regarding daniudi gas field in ordos basin, but the only novelty is they are using two extra parameters obtained from ROQSCAN (porosity and mechanical parameters) for an improved reservoir evaluation and better design for fracturing. The paper at the current stage is not acceptable but based upon this novelty, it can be reconsidered after major revisions and authors may have to re write the paper from scratch keeping below comments in mind.
Title: The only novelty of this paper is the utilization of ROQSCAN and using porosity and mechanical parameters for fine reservoir evaluation and subsequently better fracturing design. Please change the title accordingly.
Abstract:
There are a lot of grammatical mistakes. Add quantitative info about your target field and quantitative results.
Introduction:
1. Your paper reads ‘carbonate reservoir is one of the most significant domains 33 of oil and gas exploration and development, which hold more than 60% of the world’s oil 34 and 40% of the world’s gas reserves[1, 2].’
No- I know you are focussing on carbonate formation but generalizing the literature in your favour is not okay. Sandstones are the most popular domain Sandstone reservoirs typically have high porosity and permeability, which means that they can hold large amounts of oil and gas and allow it to flow easily. They are also usually easier to drill and complete compared to carbonates. Therefore, sandstone reservoirs are often favored for exploration as they are known to have higher success rates for discovery of new oil and gas fields. On the other hand, carbonate reservoirs are known for their complexity, which can make exploration and production more challenging. Now that’s why they are the primary candidates for various stimulation techniques.
Now, keep this context in mind, start your intro again, talk about the geology and then build up your story and reach to the hydraulic fracturing part. THERE SHOULDN’T BE ANY HOLES IN THE INTRODUCTION, IT NEEDS TO BE IN A FLOW.
2. ‘Dessert evaluation’ , ‘Deep shale gas dessert selection’ , in the petroleum/reservoir engineering context I never heard this term before and I believe many others won’t be familiar with this term as well. Please elaborate since you have used it throughout your into
3. What is fine identification? In which context you are using the word ‘fine’ as in fine reservoir modelling?. It is confusing.
4. Your introduction doesn’t highlight research gap but features somehow irrelevant literature references. Please provide related literature references which will help you identify the gap. Any related literature on ROQSCAN?
5. Rewrite the (last) motivational paragraph again clearly and precisely.
Research methodoldy:
1- To start with there is no methodology section. I am a firm believer of ‘your paper, your choice’ but I feel this paper has various steps and a dedicated methodology portion is imperative. Please make a flow chart of whole methodology, indicate all parameters that you will be considering.
2- Heading 2, Target well? How do you know reservoir formation and fracture development are favorable? Elaborate why just choose this one well from the whole field? And why are you choosing it at all since your motivation is not clear, so may be try to clear in this section.
How are we supposed to know MA 4,5 and 6 sections? And its relation to your target well? It needs illustration. Is Majiagou Formation your reservoir formation?
3. Heading 2.1 Physical parameter? What do you mean poor physical property?
4. Figure 1 – do your own labelling since it is supposed to be setup composition and its not adequate.
5. Section 3: Your paper reads:
‘’However, the use of seismic, logging, core and other data cannot accurately describe the reservoir characteristics, which is lack of guidance for subsequent effective reservoir fracturing. Hence, Roqscan technology with automated mineralogy tool, which can characteristic the formation at the well-site in real-time, was introduced to perform fine reservoir evaluation’
Now, according to you, Roqscan gives information about minerology and rock mechanical parameters which is not a detailed reservoir characterization since you are using it in contrast to seismic, logging, core data which provides way more information than this. I thought Roqscan was your novelty but I don’t think so it is giving enough characterization data to be considered comparable to seismic, logging, core data. Justify more, if this is your only novelty.
6. What laboratory tests you have conducted? Where is the methodology? Highlight what parameters are coming from lab test, which data are you getting from logs? And which data are you gonna use for fine modelling. Mention software and everything.
7. How ROQscan finds porosity?
Section 4: Hydraulic Fracturing:
1- More explanation on geological modelling? Parameters? Data sets needed.
2- You obtained how horizontal principal stress, porosity (just these two parameters ?) that is your novelty in this work ? are these only parameters that sets your fine model and conventional model apart? Detailed analysis on these parameters are needed. And how are they affecting the model.
3- Now you have all the mechanical parameters from ROQCAN you need but I don’t see how are you using these parameters in your fracturing design.
4. Please make a dedicated results section based upon the methodology I suggested.
Modify conclusion accordingly.
Author Response
please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript can be highly considered for publication. Yet, some issues need to be addressed by authors before can be accepted.
1. Abstract can be rewritten more concisely by directly addressing the essence of the study, main findings and significant results. In addition, please add short conclusion. I leave my suggestion to the authors for reflection.
2. Problem statement is not clear. The authors should clearly mention the gap based on the previous work in literature. Please clearly mention objectives of the study as well.
3. It is suggested to add relevant figure, photo or diagram to support the introduction.
4. The manuscript is not written in structured way. It is not clear the difference of materials and method, and results and discussion section. It seems they are mixed up in one section.
5. Please mention in details of preparation gelled acid and fracturing fluid. The detail such as concentration of material is missing.
6. The discussion of result is not comprehensive. It lacks in-depth discussion and explanation in a more detailed. It is important to provide strong discussion rather than that are simply collection and reporting the results. Current form of discussion is too brief.
7. Conclusion need to be rewritten. The conclusion need to highlight the key results to answer the objective. Please revise the conclusion accordingly.
8. The length of paragraphs which should not be too short or too long.
9. Most of the references are from one country. Should include the study by authors from other countries or regions. Moreover, please increase the number of references.
Author Response
please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
I enjoyed reading the manuscript and found the fine formation evaluation by using RoqSCAN tool and the acid fracturing to be interesting and sufficient for the conclusions written. The organization of the paper was excellent and the problem was very well motivated in the Introduction section.
I just have a few minor correction suggestions before publication.
1. In the introduction section, the authors introduce a large number of research advances in the integration of geological-engineering. I suggest that some investigations on acid fracturing can be added in the introduction section.
2. In the table 1, the number of experimental groups performed to obtain the physical parameters from testing should be introduced.
3. For the logging interpretation of target formation, the used method should be introduced.
4. The rheological property of gelled acid has been introduced. However, what’s the rheological property of slickwater？ Please add relevant content
5. For figure 12, please add some descriptions for acid-etched fracture pattern and acid-etched
6. Chinese is not recommended in the figures such as Fig. 1
Author Response
please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Dear Authors,
You have done an amazing job in reciprocating the review provided and preparing the feedback report. I can only imagine how much hard work it must have taken you to make changes accordingly. However, going through your manuscript, I found some technical mistakes which must be corrected before the acceptance of this manuscript.
Title:
What do you think about these titles?
1- Acid Fracturing Design Improvement through RoqSCAN Technology: A Case Study from Daniudi Gas Field in Ordos Basin , China.
Or
2-An Improved Acid Fracturing Design through RoqSCAN Technology: A Case Study from Daniudi Gas Field in Ordos Basin , China.
Or
3- Efficient Acid Fracturing Design using RoqSCAN Technology: A Case Study from Daniudi Gas Field in Ordos Basin, China
For the above titles suggested, please note, these are not mandatory suggestions, if you think your current title reflects your present work better, you can ignore these options, however, I strongly recommend you to add ‘China’ in the title. (Ordos Basin is in China, right?)
Abstract:
The way you have reported ‘results’ in the abstract are so vague and doesn’t reflect the true essence of the work you have conducted i.e., it sounds less scientific. The people are going to judge your work from your abstract and at the moment, I feel, it needs improvement. Please improve your results, if possible add quantitative and then subjective information.
e.g., ‘the modeling with fine reservoir evaluation has higher accuracy than the traditional modeling’ Higher accuracy? Its obvious but you can provide some related quantitative info to make sense out of it but in a concise way. Please dig a little deeper.
PS: Your conclusion contains summarized results, get inspiration from there.
1-Introduction:
i- Please put reference where you are claiming . ‘Moreover, the technology has been applied and achieved good results in Bakken Formation’
ii- Great job with highlighting the gap, however, the last motivational paragraph is still weak. Since as per your title, it is an investigation on acid fracturing but all the experiments you are conducting feels isolated (a separate research), you have to connect everything to your fracturing design as in, how the data you are getting from your experiments and ROQSCAN is gonna help you in fracture designing as you mentioned:
‘Moreover, the perforation optimization, fracturing fluid’s performance evaluation, acid fracturing numerical simulation was also performed to achieve exploration breakthrough.’
So connect this part with previous sentences so it should appear like one research , not separate research conducted.
2- TARGET WELLS
i-Consider covering it as a sub heading of introduction (this suggestion is on your discretion, as in if you think it can make better sense, do it, otherwise, keep as it is)
ii- Figure 1 is not cited in the manuscript. There is Chinese text in this figure, which is not fair for other readers who cannot read Chinese. Moreover, if this paper got accepted, in proof reading phase, the editor is going to ask you to increase the quality of this paper. I suggest, this figure will be problematic for you, so remove it.
iii. Heading 2.2, last sentence: ‘ Furthermore, the interpreted conclusion of target formation on the basis of permeability, gas-bearing and so on is gas layer and gas-bearing layer’ What are you trying to say in this sentence? Rewrite.
iv. Acknowledge in the acknowledgement section wherever you are getting this logging data from
3- RESEARCH METHOD
i. Figure 2 is wrongly cited in the text.
ii. Did you conduct in-situ core scanning of the reservoir section of the well? And core scanning from ROQSCAN? Please clarify
iii. FIGURES 5,7,8,9 – graphs don’t have x-axis and y-axis legends. Please add titles.
iv. Your results are starting from FINE RESERVOIR EVALUATION? Make a dedicated section for your results.
4- ACID FRACTURING DESIGN
i. According to Table 1 and 2, MA6 has HC content of 51-72% with 57.2% Sg while MA6 has HC content of 5-14% with 65% Sg. Since logging showed both layers contain gas, can you justify from this data, on what grounds, you chose MA5 for your fracturing design?
ii. Figure 11: In proof reading phase, the editor will ask you to add sub text of the figure, so add proper caption like (a) Porosity and mention which one is conventional and which one is fine , similarly for (b)
iii. Fig 12 and 13 are fine modelling?
iv. 5.3 fracturing design: You motivational para read that you were going to optimize perforation, but these are just one data set for all perforation parameters? Where is the optimization? Where did these preformation parameters value came from?
V. Figure 14. Put the reference in the caption, instead of writing citing from a , b or c. That’s not scientific writing. Also please rephrase the caption, it is not okay!
VI- Figure 15 – Proper subtext in the caption is needed
5- CONCLUSION
Please Improve the way you are doing numbering of the sub text after the main sentence. Use roman number or alphabets. Or just write two paragraphs, instead of scattered numbering
Author Response
please see the attachment.
Author Response File: Author Response.pdf
